The invention relates to a water discharge device designed for a system for launching objects from submerged tubes installed on board a submarine or any other type of launcher or movable or fixed submerged structure.
Known devices of this type are used in the military area to launch objects from torpedo tubes on submarines. These devices, illustrated in FIGS. 1, 2, and 3, are essentially composed of several tubes (a) for launching torpedoes (b) (a single tube is shown in the figures) with doors (c) at their ends and a slide valve (d). These torpedo tubes are connected to a water discharge device by a impulse tank (e) located outside the pressure hull (f) of the submarine (FIGS. 1 and 3), or inside the pressure hull when the size of the latter permits (FIG. 2). Impulse tank (e) forms a closed, sealed space into which the water discharge device discharges.
According to FIGS. 1 and 2, the water discharge device, called a water ram, is comprised of a pneumatic ram (g) which is located inside the pressure hull of the submarine and which drives, through a mechanical linkage passing through the pressure hull (f), a piston (h) a of hydraulic ram (i) located outside. A high-pressure compressed-air reservoir provided with a firing valve is located near pneumatic ram (g) and supplies the latter with the power necessary for launching. A line (j) extends the hydraulic ram up to the outer hull of the submarine and channels seawater drawn in from the marine environment when the hydraulic piston moves. Certain water discharge devices are equipped with a depth-pressure-resistant line and are provided with a door. A muffler is installed at the exhaust and the drain of the pneumatic ram.
European Patent Application EP 0151980 describes and claims a water ram variant that consists of replacing the pneumatic valve, supplied with compressed air, by a hydraulic ram supplied by a hydraulic fluid, coming from an air-oil accumulator. Another variant, which to date has not been reduced to practice, replaces the pneumatic ram by a linear motor.
According to FIG. 3, the water discharge device is a turbopump comprised of an air turbine (k) located inside the pressure hull of a submarine, driving a pump (m) located outside through a speed reduction unit (1). A line (n) extends pump (m) up to the outer hull of the submarine and channels the seawater drawn in from the marine environment when the pump operates. A compressed-air circuit composed of an air reservoir (o) and a firing valve (p) supplies turbine (k) when the device is implemented. A muffler is installed at the turbine exhaust.
The operating principle of these devices is described briefly below:
When a water ram actuated by a pneumatic ram is used (FIGS. 1 and 2) for a launch, as soon as the firing valve opens, the hydraulic piston driven by the pneumatic ram supplied with high-pressure compressed air from the reservoir, drives the seawater via the impulse tank to the torpedo tube in question, the slide valve of which is open. When the rear of the torpedo tube is pressurized, the weapon is ejected outside the submarine.
In the case of a device using a turbopump (FIG. 3), the firing valve supplies the turbine with compressed air, which drives the pump via the speed reduction unit. The pump drives the water taken from the marine environment to the rear of the weapon via the impulse tank and the side openings in the torpedo tube. The hydraulic pressure thus established, pushes the weapon out of the torpedo tube.
However, these devices, widely used on submarines, have a number of drawbacks inherent in their design and operating principle. For example, for launching devices using a water ram type device actuated by a pneumatic ram, these drawbacks are as follows:
1) These water ram devices are installed while the submarine is being built and before the bow is installed. These devices stay installed for the lifetime of the craft. The pneumatic ram plus hydraulic ram assembly takes up a great deal of space on either side of the pressure hull and requires an opening to be made in the hull through which the rod of the pneumatic ram slides. When not in use, keeping the device in the "armed" position exposes the mechanical link between the pneumatic ram and the hydraulic piston to stresses from the marine environment (fouling and encrustation). PA1 2) The integrity of the pressure hull is provided by dynamic seals located on the rod of the pneumatic ram, and the surface condition of this link is essential as it must not deteriorate during its translational movement because the seals ensure the watertightness of the pressure hull. This requires frequent maintenance (periodic emptying of the device while on patrol) to preserve a sufficient surface condition so as not to stress the seals. PA1 3) If the seals fail, there is nothing to prevent the seawater entering the craft if the water intake line is insufficiently strong and not equipped with a hull door. PA1 4) When the weapon is being ejected, the operation of the device causes high-speed displacement of the pneumatic ram and the hydraulic ram which are tightly nested in the internal structures and the pressure hull of the submarine. This movement brings about substantial vibrations, which are a noise source that could render the craft detectable by the enemy. During this same phase, admission of compressed air into the drive of the pneumatic ram causes substantial noise. PA1 5) During a lay-up or while the device is being prepared for a further ejection following a launch, exhausting the compressed air in the drive of the pneumatic ram, which takes place in the cramped interior of a submarine, causes the pressure in this enclosure to rise and the submarine atmosphere to cool off noticeably, especially when several ejections are effected over a relatively short space of time. This bleed causes airborne noise inside the submarine which travels across the sea, thus causing the craft to be even noisier. PA1 1) Installation of a turbopump requires a large opening to be created in the forward bulkhead of the submarine. If the turbopump has to be taken apart for maintenance, appropriate maintenance devices must be used requiring a clear passage inside the craft and clearance in the hull for the outside diameter of the mount holding the turbopump to the forward bulkhead of the submarine. PA1 2) The integrity of the pressure hull is provided by mechanical pump elements resistant to depth pressure but also by dynamic seals located on the pump drive shaft that passes through the pressure hull of the submarine. PA1 3) If the seals fail, there is nothing to prevent seawater from penetrating the craft if the water intake line is insufficiently strong and not equipped with a hull plug. PA1 4) Operation of the turbine, in addition to overpressure and cooling of the atmosphere inside the submarine due to escape of the expanded air, creates serious physiological hazards for the crew when a mass of high-pressure air expands within a very short space of time. This sudden expansion produces a very loud airborne noise that requires a large muffler if its effects are to be attenuated. PA1 1) The diameter of the hydraulic piston is increased so that its displacement speed during ejection is less than that of a hydraulic piston of a known system. PA1 2) The pneumatic ram is directly supplied by the compressed-gas reservoir, which eliminates piping and distribution systems creating pressure losses and noise source singularities. Moreover, the velocity of the compressed gas as it expands will be that of the displacement of the hydraulic piston. PA1 3) The pneumatic ram operates on the principle of an air-oil accumulator without the necessity, in a series of several successive ejections, of exhausting off the compressed gas since the device is returned to the "armed" position by the available space of the pneumatic ram being refilled with hydraulic fluid by means of a high-pressure pump. Displacement of the pneumatic piston thus re-compresses the gas reservoir. PA1 4) The assembly comprised of the pneumatic ram and the hydraulic ram, nested into each other, is located outside the pressure hull of the submarine with no links therewith other than those of mechanical attachment, fluid, electrical, and monitoring types for this assembly. PA1 5) The assembly thus created is attached to the outer structure of the submarine by mechanical elastic-type links in order to reduce transmission of vibrations to the submarine hull. PA1 6) Except for the very short phase during which the water ram is in use, while placing the pneumatic piston rod in the extended position, the rod is held in the stowed position due to the available space in the pneumatic ram being filled with hydraulic fluid and hence protected from stresses from the marine environment. PA1 7) The water ram can be uncoupled from the submarine simply by disassembling the mechanical connecting links and the fluid and electrical circuit links with minimum effort, thus allowing easier maintenance in the shop or replacement of a complete assembly in minimum time. PA1 8) The equipment installed in the pressure hull takes up limited space and does not require special maintenance equipment.
For launch devices using a turbopump, the drawbacks are as follows: